Question
I had a slope behind my house hydroseeded in August. Following the first rain a musty mildew like odor has developed. What is the cause of the odor? How long will it take to go away?

Answer
That's a tough one.  It seems to me that there's probably a lot of composting organic matter in the soil.  As it further breaks down, it gives off an odor similar to what you've described.  

As to how long this will stick around, I can't say with any certainty.  It won't be forever though, and it likely won't be for much longer.  You'll notice it more on warmer days and less on colder days.

Sorry for the predicament, but I don't think there's much to do but wait it out.

Good luck!

-C.J. Brown
www.thelawncoach.com